A fuel injector is believed to deliver fuel at specific time intervals and in precise amounts to intake valves and/or the combustion chamber of an internal combustion engine. It is further believed that fuel flowing through a fuel injector typically exits at a nozzle end of the fuel injector, and that the nozzle end typically has a disk with one or more orifices disposed thereon. It is believed that the resulting spray direction, spray particle size, spray mass flow, and spray pattern from the nozzle are a function of, among other variables, the geometry of the orifices.
An orifice is believed to be formed by drilling through a work piece that can be of any shape, including a flat piece (or disk). There are many known methods of drilling orifices for a fuel injector, including trepanning, mechanical punching and electric discharge machining (EDM). It is believed that these methods are only capable of forming orifices of 150 to 200 microns in diameter or larger. Moreover, it is also believed that these methods are incapable of forming orifices with large targeting angles. It is further believed that future low emission standards will require smaller orifices configured at significantly larger targeting angles for smaller fuel spray droplets and shorter fuel spray duration. It is therefore believed that it will be technically infeasible and/or cost prohibitive to manufacture orifices using known methods once more restrictive emission standards are adopted.
The present invention provides an apparatus that can form a plurality of orifices that are dimensionally consistent, such as, for example, the diameter, the surface roughness or the entry and exit configurations. In a preferred embodiment, the invention provides a laser machining apparatus. The apparatus includes a laser light source that provides a generally coherent light beam along the beam""s axis. The apparatus also includes a light directing device to direct a first portion of light from the light beam to a work piece at a first angle of incidence relative to the beam""s axis during a first time interval to form at least one of an orifice and a chamfer. The apparatus further includes an adjustable beam splitter assembly to direct another portion of the light beam to form the other of the at least one of an orifice and a chamfer in the work piece during a second time interval that overlaps a portion of the first time interval.
The present invention additionally provides a method of forming at least one orifice in a workpiece and also machining the entry or exit surfaces (e.g., a chamfer) of the orifice at or about the same time as the orifice is formed. The at least one orifice is disposed along a longitudinal axis extending between a first surface and a second surface of a workpiece. The chamfer is disposed proximate at least one of the first surface and the second surface. In another preferred embodiment, the method can be achieved by providing at least a first beam and a second beam that are emitted from the laser light source towards the workpiece; rotating at least a first beam and a second beam with respect to the longitudinal axis; forming at least one orifice in the workpiece with at least one of the first and second beams during a first time interval; and forming the at least one chamfer in the workpiece with the other of the first and second beams during a second time interval that overlaps a portion of the first time interval.